Dear Sirs,

We presently have a 316L matl 3/8" wall thk. cyclone separator (F&D head & cone bottom) that the Client has speced out to API 620 Code. The operating temp is 215 deg F and design temp is 300 deg F, op pressure is 3 psig to 5 in. wc vacuum and design pressure is 7.5 psig to 15 in. wc vacuum.

Client test reqs are 10 psig hydro and spot RT w/ 85% jnt efficiency.

API 620 states in 5.26 Radiographic/Ultrasonic Examination
5.26.4.3 (a) When parts of tanks do not require complete examination, circumferential joints in cylindrical or conical surfaces need to be prepared and examined for a distance of only 3 in. on each side of any intersection with a longitudinal joint. All joints in a spherical, torispherical, or ellipsoidal shape or in any other surface or double curvature shall be considered longitudinal joints.

Does this mean that ALL "T" type joints (circ.-to-long seams) require RT?

Appreciate your interpretation and comments,
Robert

One recent interpretation that has been presented to me is as follows: Example vessel contains 120 feet of linear weld seam with 12 "T" joints:

7.17.3 Number and Location of Spot Examination
7.17.3.2 At least one spot shall be examined from the first 10 ft of completed joint of each type and thickness welded by each welder or welding operator. Thereafter, without regard to the number of welders or welding operators involved, one additional spot shall be examined for each additional 50 ft - or remaining fractional part of this length - of each type and thickness of welded longitudinal, meridional, or equivalent joint subject to examination. The inspector shall designate the locations of all spots that are to be examined, of which at least 25% of the selected spots shall be at junctions of meidional and latitudinal joints with a minimum of two such intersections per tank (see 7.15.6.2), both under the foregoing provisions and the provisions of 7.17.3.4. Such spots need not have any regularity of spacing.

7.17.3.4 Whenever spot examination is required for circumferential or latitudianal joints other than those considered in 7.17.3.2 and 7.17.3.3, one spot shall be examined from the first 10 ft of completed joint of each type and thickness welded by each welder or welding operator if not already done on other joints for the same welder or welding operator on the same structure.

(7.17.3.2 At least one spot shall be examined from the first 10 ft of completed joint)
First RT shot would be taken in the first 10 feet of weld,

(one additional spot shall be examined for each additional 50 ft)
second shot taken between 10 ft and 60 ft,

(one additional spot shall be examined for each additional 50 ft)
third shot taken between 60 ft and 110 ft,

(one additional spot shall be examined for each additional 50 ft - or remaining fractional part of this length)
fourth shot taken betw 110 and 120 ft (the remaining fractional part).

(The inspector shall designate the locations of all spots that are to be examined, of which at least 25% of the selected spots shall be at junctions of meidional and latitudinal joints)
25% of these 4 shots must be "T" joints therefore equals 1 "T" joint shot,

(with a minimum of two such intersections per tank)
however code states a minimum of 2 such intersections per tank therefore of the 4 shots total with 2 of these being "T" joints.

Does this make sense to you? Appreciate your comments,,
Robert

Robert,
(7.17.3.2 At least one spot shall be examined from the first 10 ft of completed joint)
First RT shot would be taken in the first 10 feet of weld,

This is applicable if only one welder - if more than one welder your 2nd, 3rd, 4th shot etc could be in the first 10ft of each welder.

(The inspector shall designate the locations of all spots that are to be examined, of which at least 25% of the selected spots shall be at junctions of meidional and latitudinal joints)
25% of these 4 shots must be "T" joints therefore equals 1 "T" joint shot,

You state earlier in the post there are 12 T joints - where does the 4 T joints come from ?

Regards,
BB

7.17.3.2 At least one spot shall be examined from the first 10 ft of completed joint)
First RT shot would be taken in the first 10 feet of weld,

(one additional spot shall be examined for each additional 50 ft)
second shot taken between 10 ft and 60 ft,

(one additional spot shall be examined for each additional 50 ft)
third shot taken between 60 ft and 110 ft,

(one additional spot shall be examined for each additional 50 ft - or remaining fractional part of this length)
fourth shot taken betw 110 and 120 ft (the remaining fractional part).

4 shots total, 1 of which has to be a T joint to satisfy the 25% requirement, but a minimum of 2 T joints per tank, thus a total of 4 shots with 2 of these being T joints.